Endoscopic surgery is a minimally invasive therapeutic and/or diagnostic procedure during which relatively small visualization and surgical tools are introduced into a portion of the human body such as a knee joint through relatively small incisions. Typically, at least three incisions are employed for a therapeutic procedure and at least two are employed for a diagnostic procedure. During endoscopic surgery, physiological fluid such as a sterile saline solution is allowed to flow through the joint so as to distend the joint to facilitate access to the joint. In addition, the flow of physiological fluid through the joint enhances the clarity of the field of view by removing debris from the surgical site.
The flow of fluid into the joint during endoscopic surgery is regulated by two independent but yet related functions. These two functions are the pressure of fluid within the joint and the volume of fluid flowing through the joint. The pressure of fluid within the joint determines the extent to which the joint is distended. For example, a surgeon may want to increase the pressure of fluid within the joint when the surgeon needs to view or access the end of the joint opposite to the point of insertion of the probe. In contrast, if there is bleeding or debris in the cavity, an increase in the flow rate of fluid is needed to clear the field of view. In addition, when an instrument such as a shaver with a suction tube is used, a greater flow of fluid into the cavity is required to prevent the cavity from collapsing.
Various methods are known to control the pressure and flow rate of fluid during endoscopic surgery. These methods range from certain manual methods, such as manually adjusting the height of fluid supply bags to increase pressure while maintaining flow rates using variable clamps on the tubing leading to and away from the patient, to automatic fluid control systems. Some of these automatic fluid control systems regulate flow rate in response to the sensed pressure corresponding to the pressure within the cavity. Other automatic fluid control systems attempt to maintain a constant volume of fluid flowing into the cavity and therefore a constant pressure within the joint by balancing the inflow and outflow of the physiological fluid into the cavity. Still other of these automatic fluid control systems allow for independent control of the flow rate and the pressure, allowing the system to operate at a specified number of fixed flow rates and fixed pressures.
The equipment used for endoscopic surgery in the past has been relatively difficult to use. For example, a nurse generally has to connect individual tubes to various cannulas and pumps associated with the system as well as to thread tubes through peristaltic pumps. This is a relatively time consuming activity. In addition, the surgeon often has to adjust the pump speed each time the shaver is used. This is because the shaver will draw fluid from the cavity thereby requiring the surgeon to increase the flow rate of fluid into the cavity. In addition, the light source for illuminating the cavity is functionally independent of the camera used to record the image inside the cavity. Accordingly, the surgeon has to white balance the camera in order to provide a relatively clear image. In addition, because the endoscopy system is typically shared between different surgeons, the various parameters such as flow rate, cavity pressure, shaver speed and so forth have to be readjusted virtually every time a doctor begins using the equipment after another doctor has finished using the equipment.
In addition to the foregoing, the equipment used for performing surgery often uses a shaver handpiece which is subject to certain disadvantages. For example, the shaver handpiece is often driven by a motor which is connected by a gear box to the shaver blade. Not only does the presence of the gear box complicate the construction of the shaver, the gears within the gear box could fail upon receipt of excess torque also tended to cause premature failure of the shaver handpiece. In addition, because the flow of debris through the shaver handpiece does not often follow a straight path, the debris will often plug the shaver handpiece making the handpiece inoperable.